What: wordnet

 Where: http://wordnet.princeton.edu/
 Description: Online lexical reference system.
        A lexical database for the English language
 Updated: 12/2006
 Contact: mailto:wordnet@princeton.edu

That is, a dictionary.

There is an online version [1] and an off-line version [2]. The off-line version is avalable for Windows and Unix.

It is mentioned here because it is based on Tcl/Tk. Don't expect too much. It works, but is rather poorly designed.

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